lambda: scalar, usually (but not necessarily) on the interval 0,1.
C: matrix probably returned by vcv.phylo.
Details
Multiplies the off-diagonals of a square matrix by lambda and returns the result.
Returns
Typically an among-species phylogenetic variance covariance matrix (e.g., vcv.phylo) in which the off-diagonal elements have been multiplied by lambda.
References
Revell, L. J. (2024) phytools 2.0: an updated R ecosystem for phylogenetic comparative methods (and other things). PeerJ, 12 , e16505.